[Highland Park] gunshots this morning

I live on Wayne Rd. with my backyard on Jackson, very near the Jackson and N. Euclid intersection. At 4 p.m. this morning, we heard a series of gunshots that seemed to come from a semi-automatic hand gun. The shots were so loud, and so distinct, they seemed as if they were right in my backyard. I heard no cars, no people, and never heard police sirens. Did anyone else hear this? Anyone know what was going on? It was very, very frightening..... Maryann Moore